This invention is related generally to fiber optics and optical switching systems. In particular, the invention is related to Micro-Electro-Mechanical system (MEMS) design and fabrication.
A MEMS device is a micro-sized mechanical structure having mechanical circuitry fabricated using conventional integrated circuit (IC) fabrication methods. A well-known MEMS device is a microscopic gimbaled mirror mounted on a substrate. A gimbaled mirror is a device that may pivot on a hinge about an axis. By pivoting about an axis, a gimbaled mirror can redirect light beams to varying positions. Typically, MEMS gimbaled mirrors are arranged in an array on single silicon wafer substrate.
Fabrication of micro-mirror array chips used by a MEMS device requires precise alignment between the MEMS structure and other optical components such as optical fiber arrays or laser arrays. During the fabrication a MEMS device, it is often necessary to bond one part of the MEMS device found on one wafer to another part of the device that is formed on a different wafer. Conventionally, these multiple layers of a MEMS device are aligned using a xe2x80x9cflip-chipxe2x80x9d optical alignment system to align the two wafers, or two parts, to each other. Fixtures are used to hold the wafers together, then the wafers are attached to each other.
This alignment process for joining the two wafers is therefore an active alignment process. The active alignment process requires a laser beam generating system and a laser beam detection system to check the optical alignment of the wafers. The MEMS components are aligned in position when the optimal optical coupling between the laser beam generating system and the detection system is achieved.
This prior solution relies on expensive machines and is time consuming. It is difficult to achieve high precision alignment between two wafers, or components, of the MEMS device because the fixtures used to hold the wafers in place may cause alignment shift. It is also difficult to align the MEMS system with another optical system such as a fiber array or lens array using this active alignment process. Furthermore, conventional bonding processes often rely on heat to bond the two wafers together. However, if one wafer has a thermal expansion coefficient that is different than the thermal expansion coefficient of the other wafer, then the heat bonding process will cause one wafer to expand more than the other wafer. As a result, one or both of the wafers will be distorted.
A micro-electro-mechanical-system (MEMS) mirror device passive alignment fabrication method is disclosed. In one embodiment, the method includes forming a release layer on a first substrate, forming a mirror pattern having a center mirror component and a hinge pattern supported by the release layer, forming a first passive alignment mechanism on the first substrate, forming an electrode layer on a second substrate, forming a second passive alignment mechanism on the second substrate, aligning the first and second substrates using the first and second passive alignment mechanisms, and attaching the first substrate with the second substrate by inserting a passive non-thermal bonding mechanism through the first and second passive alignment mechanisms.
Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows below.